Design and fabrication of autonomous electronic lablets for chemical control

The programmable investigation and control of chemical systems at the microscale has been an increasingly successful area in microsystem technology for over 25 years including our own work in lab-on-a-chip and microfluidics to approach electronic chemical cells [1-2]. These systems require and are limited by their physical connection (wires, tubes, pipetting) to the macroscopic control system, both for electrical and chemical interfacing. Wireless electronic systems, communicating using radio waves, although already advocated for smart dust [3-4] and implemented down to mm scales, are not yet effective at 100 µm scales and below, especially in aqueous solution where communication is damped, and also do not provide a solution for powering smart microscopic electronic particles in solution. Our approach is a novel and more chemically inspired one [5] - to take advantage of the mobility of microscopic particles which allows their docking to one another pairwise or to a smart microstructured surface (called the dock). It involves fully programmable CMOS electronic particles in contrast to other more restricted approaches such as plasmonic smart dust [6]. Electronic integration using CMOS has been optimized for high speed (GHz range) operation and high integration levels with feature sizes down to 30nm and below. However, for microscopic electronics, extremely low power operation is required (total average power, typically 1 nW for 1000s) by current microscopic charge storage limitations ( 2 µF using supercap technology), which is not consistent either with high frequency operation or the leakage currents associated with the finest scale transistors. Instead, low power operation has been achieved using 180nm technology and an especially designed slow clock [7] and custom transistor design. Electronic actuation of chemical reactions mostly requires switching of voltages on microelectrodes in aqueous solution, which typically have significant capacitances, as exploited in electrolyte capacitors.